The metal surface of laser heat treatment is generally processed by mechanical processing, with small surface roughness and high reflectivity to laser. Before laser heat treatment, the quenched surface should be pre treated to improve its absorbance. After oil removal, rust removal, cleaning, and drying of the treated surface, a light absorbing coating (blackening) is pre installed on the surface. The methods include phosphating, spraying (brushing) paint, improving surface roughness, oxidation, coating, etc; The coating should be thin, uniform in thickness, with a high laser absorption rate (over 90%), good thermal conductivity, good adhesion to metal, and not decompose or evaporate at a certain temperature. It is easy to clean and remove after quenching or can be used without removal.

Laser heat treatment, also known as laser quenching or laser phase transformation hardening, is a process in which a high-energy laser beam is used to quickly scan the workpiece, causing the surface temperature of the irradiated metal or alloy to rise above the phase transformation point at an extremely fast rate. When the laser beam leaves the irradiated area, due to thermal conduction, the cold substrate rapidly cools down and undergoes self cooling quenching to obtain a finer hardened layer structure, with a hardness generally higher than that of conventional quenching.